In endless belt conveyor installations, the usual practice is to have loading stations at definite locations for deposition of the material to be conveyed. The belts extend in many cases several hundred feet. Because of their length and construction, they are extremely expensive. The nature and structure of these belts often render them susceptible to damage by the materials they convey. This damage often occurs at the loading station of the belt conveyor where the materials strike the belt with considerable impact and where there is not sufficient means to cushion the shock.
To protect the belt against such damage, impact absorbing idler assemblies having impact roller structures are usually placed along the conveyor at places of high impact or shock loads. In some instances the idler assemblies may extend the entire length of the conveyor.
Generally, the impact idler assemblies are made as light as possible. However, the impact idler assemblies which support the belt in the region of the loading stations are subjected to considerably heavier abuse than those assemblies which merely support the load as it is being carried along by the belt.
Early in the art, the roller portions of the impact idler assemblies were composed of a deformable material such as rubber which was frequently wrapped around a steel roller shell so as to provide additional absorption characteristics. However, such impact roller structures were found to not afford enough cushioning to do an adequate job of impact absorption due to a lack of provision for the rubber to flow or deform. The individual impact roller structures in the impact idler assemblies were found to become permanently deformed under the impact of material which was deposited onto the belt. Permanent deformation of the impact roller assemblies is undesirable because it displaces the center of gravity of the roller assemblies away from the roller axis. Consequently, the roller wobbles. As the roller wobbles, it takes on the characteristics of an eccentric. The bearings, therefore, wear at a much faster than normal rate, thus shortening the life of the bearings and other roller components.
Wobbly rotation of the rollers also tends to increase the power requirement because of the eccentric characteristics of the roller. Roller wobble may also result in a variation in the magnitude of the frictional force between the belts and the roller, and thereby variations in the driving force between the belt and the roller assemblies. Further, impact rollers whose masses are displaced from free rotation also tend to wear at a more rapid rate due to the generation of internal heat and friction. Various prior attempts to overcome these undesirable effects have been made.
As the art advanced, slots or grooves were formed in a thick rubber ring to permit substantial deflection, and having energy absorbing capacity many times that of the first, smooth rubber covered rollers. The diameters were enlarged and the width of the area between the grooves was narrowed to provide a maximum degree of impact absorption. But, to provide a full range of impact rollers, a great many sizes have to be stocked.
To solve this problem, a series of tire-like elements or segments made of yieldable elastomer have been mounted on a rotatable shaft in a sufficient quantity to equal the widths required. This design, however, presents a difficulty in mounting the segments to the shaft. Often, one or more of these segments will loosen, and friction caused by slippage will soon destroy the segment and present a serious danger to the belt.
To allow greater deformation and therefore greater impact absorption by the idler, tire-like segments were narrowed at the circumference to small tapering tips. This leaves a large proportion of the belt unsupported by the idler and imposes excess shear loads on the belt carcass.
The present invention with its many advantageous features solves many of these problems.